1. Field of the Invention
The present invention relates to a technique whereby, when a sand core for casting is installed in a mold, problems such as displacement of the sand core within the mold, an unnecessary clearance gap formed between the sand core and the mold, and possible damage of the sand core itself can be prevented for stable installation.
2. Description of the Prior Art
According to a conventional technology, a sand core for casting is generally installed in a mold by fitting a fitting section, such as a concavity and a convexity provided on a skirting base section of the sand core in a place other than a product section, into another fitting section such as a concavity and a convexity of the mold. In the case where the fitting sections such as a concavity and a convexity are provided in two remote locations, if the clearance between the fitting sections is small, there is some possibility that the core will be damaged because excessive force is applied to the core when the mold is deformed by thermal expansion. On the other hand, if the clearance is large, there is a problem in that the shape of the product is adversely affected because, when molten metal flows into a cavity, the core floats up, the molten metal gets into a gap formed by the floating core, or the core is displaced to cause a nonuniform phenomenon. To solve such a problem, a technique is known whereby a projected rim of an inverted V-shaped cross section is provided at a contact section between the skirting base section and the mold and when the mold sections are closed to hold the skirting base section therebetween, the projected rim is deformed to absorb the dimensional error (for example, refer to Patent Document 1).
On the other hand, a technique, whereby a dust storage groove is provided in a recess of the mold to prevent the dust within the recess from forcibly entering the cavity, is also known (for example, refer to Patent Documents 2 and 3).
Patent Document 1: Japanese Patent No. 3320912
Patent Document 2: Japanese Utility Model Publication No, Sho 63-2197
Patent Document 3: Japanese Unexamined Utility Model Publication No. Hei 4-129550
However, in such a technique as disclosed in Patent Document 1, there is a problem in that, when the projected rim is deformed to absorb the dimensional error, if the sand from the deformed place drops, the sand forcibly enters the cavity to cause the quality of a molded product to deteriorate. There is also a problem in that, since the skirting base section is held by surrounding its periphery by the upper mold, in the case where a pressing force is applied to the projected rim to push it onto the skirting base section side, the skirting base section is damaged if it is thin.
Further, in the techniques as disclosed in Patent Documents 2 and 3, there is a problem in that the mold structure becomes complicated and fabrication costs of the mold become high because the mold must be provided with the dust storage groove, and an operation is troublesome because the sand and the like must be regularly removed from the dust storage groove of the mold.